I don’t get it.

EDIT:

YOU can evade them, but most people can’t.

It’s some weird % math. Sending BS spam, like the good old nigerian prince, costs nearly nothing, but it only needs to work in like 1 in 10 million cases for it to be profitable. Returns on random spam advertisement is abysmal, and google gets like 10-100x that because it’s more targeted. That is why people use google ads. But also not because they’re good. They’re just less useless, while still having a very very minimal effect.

The rest is scale.